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Full text of "Text Book Of Mechanical Engineering"

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1148

Appendix VI.

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Pp. 6pj #72^ gio. Serve Tubes. — M. Sauvage finds that
these boiler tubes give 2\ times the evaporation of smooth tubes.
The heating surface of a plain tube being -92, that of a Serve tube
of same size is n8, so the heating surface is increased nearly 30%,
and the efficiency in a greater ratio. The cost of a Serve tube is
2\ times that of a smooth one, however.

' Pp. 693 and p/o. Calorific Value of Fuel.—The Darling
Coal Calorimeter is a great improvement on other forms, and is
most perfect in action. A glass vessel K, Fig. 1017, contains the
water to be heated, and is sometimes protected from air currents
by being enclosed within a second jar L. The apparatus consists
of a glass bell-jar B, attached to a plate E, which supports the

FJUQ, 1017.

platinum or nickel crucible A, containing a weighed sample of the
coal to -be burnt. The bell-jar and stand, supported by the legs
F, carry also the loose fitting G H, which consists of a tube G and
a thin drum H, having holes in its upper surface for the discharge
of gas-bubbles. An oxygen bottle with hand-valve adjustment is
coupled to the brass pipe D, passing through the india-rubber
stopper Cj and a thermometer j completes the outfit To use the
calorimeter, a sample of coal is ground to powder and weighed